Process for the production of synthetic resins which contain urethane groups

ABSTRACT

A process is provided for the production of synthetic urethane resins from polyhydroxyl compounds, polyisocyanates organic, flame protective agents and, if desired; blowing agents and other additives in which N-methylol compounds of the structure WHEREIN THE Acyl radical represents a -COH, -COR&#39;&#39;&#39;&#39;, -COOR&#39;&#39;&#39;&#39;, SO2R&#39;&#39;&#39;&#39;, -SO2R&#39;&#39;&#39;&#39;&#39;&#39; or -PO(OR&#39;&#39;&#39;&#39;)2 radical in which R&#39;&#39;&#39;&#39;is a C1 to C18 alkyl radical and R&#39;&#39;&#39;&#39;&#39;&#39; is a C6 to C14, preferably C6, aryl radical, R and R&#39;&#39; are hydrogen or a C1 to C4 alkyl radical and n is an integer of 1 to 3 are used in a quantity of from about 1 to about 20 percent by weight based on the quantity of polyisocyanate.

United States Patent Diehr et al.

[54] PROCESS FOR THE PRODUCTION OF SYNTHETIC RESINS WHICH CONTAINURETHANE GROUPS [72] Inventors: Hans Joachim Diehr; Rudolf Merten;Konrad Uhlig, all of Leverkusen, Germany [73] Assignee: FarbentabrikenBayer Aktiengesellschaft,

Leverkusen, Germany [22] Filed: Jan. 19, 1970 [21] Appl.No.: 4,028

[30] Foreign Application Priority Data Jan. 29, 1969 Germany ..P 19 04232.1

[56] References Cited UNITED STATES PATENTS 3,491,067 1/1970 Sellet..260/77.5X 3,397,184 8/1968 Heydkamp ..260/2.5X

[ 51 Feb. 22, 1972 3,240,729 3/1966 Hoye ..260/ 2.5 3,222,305 12/1965Lanham t ..260/2.5 3,061,557 10/1962 Hostettler... ..260/2.5 3,255,1316/1966 Ahlbrecht .260/77.5 X 3,385,801 5/1968 Birum ..260/2.5

Primary Examiner-Donald E. Craja Assistant Examiner-C. Warren IvyAttorneyRobert A. Gerlach and Sylvia Gosztonyl [57] ABSTRACT A processis provided for the production of synthetic urethane resins frompolyhydroxyl compounds, polyisocyanates organic, flame protective agentsand, if desired; blowing agents and other additives in which N-methylolcompounds of the structure are employed wherein the Acyl radicalrepresents a COH.

radical in which R" is a C to C alkyl radical and R is a C to C14,preferably C aryl radical, R and R are hydrogen or a C to C alkylradical and n is an integer of l to 3 are v used in a quantity of fromabout 1 to about 20 percent by weight based on the quantity ofpolyisocyanate.

7 Claims, No Drawings PROCESS FOR THE PRODUCTION OF SYNTHETIC RESINSWHICH CONTAIN URETI-IANE GROUPS Urethane containing synthetic resinshaving a wide variety of different types of physical properties, andparticularly foam urethane resins, can be prepared by the isocyanatepolyaddition process. In the polyaddition reaction compounds containingat least two hydrogen atoms reactive with isocyanate groups,particularly hydroxyl and carboxyl groups, are reacted withpolyisocyanates in the presence of activators, stabilizers and otheradditives. In those cases in which a foam plastic is to be prepared,water and/or other blowing agents are added to the formulation in orderto impart a cellular structure to the final product.

In the production of polyurethane resins, including foams, it had beenknown heretofore to add components to the reaction mixture which wouldimpart some degree of nonflammability to the final product, even to theextent that the product becomes self-extinguishing. The flame inhibitingsubstances which have been used are generally compounds which containphosphorus, halogen atoms, antimony and the like, either alone or incombination with other additives. The flame retardants which have beenemployed are of two distinct types: those which will build into thepolymeric structure and those which are present merely in admixture withthe polymer. In

the first case, the additives contain functional groups which react withcomponents of the polyurethane reaction mixture with the result that theadditive becomes built into the synthetic resin structure; examples ofsome such compounds include halogenated isocyanates, phosphoric estersand so on. The additives of the second group are present merely inadmixture with the polymers because they do not contain functionalgroups; examples of some such additives include halogenatedhydrocarbons, phosphorus compounds which do not contain functionalgroups and so on. When a sufficient quantity of such additives areemployed to ensure that the polymer is substantially nonflammable, themechanical properties of the resin becomeimpaired.

It is, therefore, an object of this invention to provide flame resistantpolyurethanes and a method for their preparation which are substantiallydevoid of the foregoing disadvantages.

It is a further object of this invention to provide flame resistantpolyurethanes and a process for their production wherein the flameproofing ability of prior art flame retarding additives is significantlyincreased and even often doubled.

Another object of this invention is to provide flame resistantpolyurethanes which have improved mechanical properties and a processfor preparing them.

An additional object of this invention is to provide nonflammablepolyurethane foam products which are especially useful in the productionof hard, semihard and flexible molded foam products.

The foregoing objects and others which will become ap parent from thefollowing description are accomplished in accordance with thisinvention, generally speaking, by providing polyurethane resins and aprocess for preparing them in which polyhydroxyl compounds are reactedwith organic polyisocyanates in the presence of a flame-retardingadditive and, if

desired, a blowing agent and other additives wherein from about 1 toabout 20 percent, preferably 1 to 15 percent, by weight based on thequantity of organic polyisocyanate present of an N-methylol compoundhaving the structure like, but preferably phenyl, R and R representhydrogen atoms or an alkyl radical having one to four carbon atoms suchas, for example, methyl, ethyl, propyl, butyl, and n is an integer of 1to 3.

Surprisingly, it has been found that the flame resistance ofpolyurethane resins, particularly polyurethane foams, which containflame proofing agents known in the art can be considerably improved whenthe N-methylol compounds of this invention are added to the polyurethanemixture. Indeed, in the torch test of polyurethane foams produced inaccordance with this invention, the complete combustion times for thepolyurethanes of this invention are substantially increased and ofteneven doubled when compared to polyurethane foams produced from identicalreaction mixtures which do not contain the N-methylol of this invention.Even further, a demonstrable improvement can be observed in themechanical properties of polyurethane products produced in accordancewith this invention. Due to their free hydroxy groups the N- methylolcompounds react with the polyisocyanate und r formation of urethanegroups.

The N-methylol compounds of this invention can usually be prepared fromamides having the formula Acyl-NH-R wherein R and Acyl are as alreadydefined. These amides are heated to the melting point, e.g., to 60-240preferably to 200 C. in the presence of basic compounds such as alkalimetal hydroxides, alkali metal carbonates and alkaline earth metaloxides, with aldehydes of the formula R'--CHO in which R is as alreadydefined. Examples of some such aldehydes include paraformaldehyde,trioxane, acetaldehyde, propionaldehyde, butyraldehyde and the like andpreferably those which contain one to six carbon atoms. Some suitableamides which may be used as starting materials in the preparation of theN-methylol compounds of this invention include alkyl and aryl amidessuch as acetamide, chloroaeetamide, dichloroacetamide, butyramide,dodecanecarboxylic acid amide, octadecanecarboxylic acid amide,benzamide, 4- chlorobenzamide, a-naphthoic acid amide, formamide,benzene sulphonic acid amide, ptolu,enesulphonic acid amide,methanesulphonic acid amide, phosphoric acid diethyl ester amide,N-methylacetamide, N-butylacetamide, N- methylbenzamide,N-butylbenzamide, N-butylbenzenesulphonic acid amide,N-methylmethanesulphonic acid amide and the like and preferablythosewhich contain one to 20 carbon atoms. The preferred methylolcompounds are those which can be easily dosed and mixed with the otherreactants, and, hence, those which are liquid at room temperature.

Suitable polyhydroxyl compounds to be used in the practice of thisinvention usually have molecular weights of from about 800 to about3,000 including polyesters, polyethers, polythioethers, polyester amidesand the like which contain several hydroxyl groups such as those knownfor theproduction of homogeneous or cellular polyurethanes and.disclosed in US Pat. No. 3,201,372. Suitable hydroxyl polyesters are,for example, reaction products of ,polyhydric alcohols with polybasiccarboxylic acids. Instead of the free carboxylic acids,- thecorresponding polycarboxylic acid ,anhydrides, polycarboxylic acidesters or mixtures of these compounds may be used for the preparation ofthe hydroxyl polyesters. The polycarboxylic acids may be aliphatic,cycloaliphatic, aromatic or heterocyclic compounds and maybe substitutedand/or unsaturated. Succinic acid, adipic acid, sebacic .acid, phthalicacid, phthalic acid anhydride, maleic acid, maleic acid anhydride,monomeric, dimeric and trimeric fatty acids, dimethylterephthalate andthe like aregiven as individual examples.

The alcohol component may, for example, be ethylene glycol, propyleneglycol-(1,3), butylene glycol-(1,4), and (2,3), glycerol, hexanetriol-(1,2,6), butanetrio-(l,2,4), trimethylolpropane, trimethylolethane,pentaerythritol, mannitol, sorbitol and the like and polyethyleneglycols,

polypropylene glycols, polybutylene glycols and the like as disclosed inU.S. Pat. No. 3,201,372. The hydroxyl polyethers which are suitable forthe invention are also known and can be prepared, for example, by thepolymerization of epoxides such as ethylene oxide, propylene oxide,butylene oxide, styrene oxide, epichlorohydrin and the like, if desiredwith starting components which have reactive hydrogen atoms, such asalcohols or amines, e.g., glycerol, trimethylol propane, ethyleneglycol, ammonia, ethanolamine and so on. Sucrose polyethers may also beused, Numerous representatives of the polyhydroxyl compounds which maybe used in this invention are described, e.g., in Saunders and Frisch,Polyurethanes, Chemistry and 'Iechnology, Volumes I and II, lntersciencePublishers I962 and 1964 (page 32f Volume I and page 5 and page l98fVolume II) and in Kunsrsloff-Handbuch, Volume VII, Vieweg-Hochtlen,Publishers Carl Hanser Verlag, Munich 1966, e.g., on pages 45-71. Lowmolecular weight polyhydroxyl compounds, e.g., of the type alreadymentioned and/or chain lengthening agents such as glycols, diamines orwater may also be used to a certain extent and are also disclosed inU.S. Pat. No. 3,201,372.

The organic polyisocyanates may be of any desired type, e.g., aliphatic,cycloaliphatic, araliphatic, aromatic, divalent and higher valent,including alkylene diisocyanates such as tetraand hexa-methylenediisocyanate, arylene diisocyanates and their alkylation products suchas phenylene diisocyanates, naphthylene diisocyanates, diphenylmethanediisocyanates, toluylene diisocyanates, diand tri-isopropylene benzenediisocyanates, triphenylmethane triisocyanates,p-isocyanatophenyl-thiophosphoric acid triesters,p-isocyanatophenylphosphoric acid esters, aralkyldiisocyanates such asl-(isocyanatophenyl)-ethyl isocyanate, the xylylene diisocyanates,polyisocyanates which have been substituted by all sorts of differentsubstituents such as alkoxy, nitro, chlorine, bromine and the like, andpolyisocyanates which have been modified with subequivalent quantitiesof polyhydroxyl compounds such as trimethylolpropane, hexanetriol,glycerol, butane diol, any of those suggested herein and so on. Suitablepolyisocyanates also include those obtained from Schiff's bases of thegeneral formula in which formula R represents an n-valent C ,C.,-alkylradical such as methyl, ethyl, propyl, or butyl, an n-valent C -Ccycloalkyl radical such as cyclo pentyl, cyclohexyl or methylcyclohexyl, an n-valent C -C -aryl radical such as phenyl, methylphenyl, dimethyl phenyl, trimethyl phenyl, naphthyl, methyl naphthyl ordimethyl naphthyl or an n-valent C -C aralkyl radical such as phenylmethyl, methyl phenyl methyl, dimethyl phenyl methyl or napthyl methylwhich radicals may be interrupted by hetero atoms such as oxygen,nitrogen or sulphur, R represents an aryl, cycloalkyl, aralkyl or arylradical as defined above, R and R represent a hydrogen atom or an alkylcyclo alkyl, aralkyl or aryl radical as defined above, R and R maytogether represent a 5- to 7-membered isocyclic or heterocyclic ring andn represents an integer of l to 3. The polyisocyanates are obtained byreacting the Schiffs base at a temperature of 30 to 250 C. withpolyisocyanates ofthe general formula in which R is an x-valent alkyl,cycloalkyl, aralkyl or aryl group as defined above and x is the integer2 or 3.

Any of the polyisocyanates prepared by condensing aniline withformaldehyde followed by phosgenation are especially advantageous. Otherexamples include polyisocyanates masked with phenols, oximes orbisulphite, acetal-modified isocyanates, polymerized isocyanatescontaining isocyanurate rings, higher molecular weight polyisocyanatesprepared by reacting monomeric polyisocyanates with higher molecularweight compounds containing reactive hydrogen atoms, preferably highermolecular weight polyhydroxyl compounds, polycarboxyl and polyaminocompounds, and the like and mixtures thereof. Diphenylmethanediisocyanates which contain carbodiimide groups, such as those which canbe prepared, e.g., according to German Pat. No. 1,092,007 may also beused as well as mixtures of different isocyanates.

Other components used in the practice of this invention include flameinhibiting substances of the type already known in the art whichgenerally contain phosphorus and halogens either alone or incombination. in addition, other flame protective agents may be used,e.g., antimony compounds, bismuth compounds, boron compounds and thelike. Further suitable flame protective agents known in the art aresuggested in the chapter Flammhemmende Substanzen" on pages to 111 inKunststoff-Handbuch, Volume 7, Polyurethanes, by Vieweg-Hdchtlen,publishers Carl Hanser-Verlag, Munich 1966. Particularly suitable flameinhibiting substances are e.g.,

(a) phosphorus and nitrogen containing compounds such as 1 (H C0) iOH2N(CH:CH 0H)g H (C 115O)zP-CH2N(CHr-CH:OH)2

(b) phosphorus and halogen containing compounds such as O=P(OCH CH2X)aX=Ci, Br

(c) phosphoric acid resp. phosphonic acid esters such as R 0=P-(0CH2-H-OH)2 R=CH 0 H,

r, C2 5, CaHin (d) halogen containing substances such as 0 Br H lC-,O-CHz H-OH -Br C1- CO-OR Hexabromcyclododecatrien The flameinhibiting substances are generally included in quantities of l to 20percent by weight, preferably 1 to percent by weight, based on thequantity of isocyanate used.

The process of this invention is directed to the production ofhomogeneous polyurethanes, preferably polyurethane foams. In order toproduce polyurethane foams, it is necessary to include water and/orother blowing agents in the reaction mixture. Some suitable blowingagents include, generally, alkanes, halogenated alkanes or low boilingsolvents, e.g., methylene chloride, monofluorotrichloromethane,difluorodichloromethane, acetone and the like as well as those listed inU.S. Pat. No. 3,201,372 and mixtures thereof. Compounds which alsoliberate gases at elevated temperatures such as azo compounds may alsobe used as blowing agents. The production of synthetic resins whichcontain urethane groups, especially foam plastics, is otherwise carriedout by processes which are known per se, either manually ormechanically, and known additives such as activators, emulsifiers,stabilizers, pigments and dyes and fillers, e.g., as listed in U.S. Pat.NO. 3,201,372, may be added. Suitable activators include tertiary aminessuch as triethylamine, dimethylbenzylamine, tetramethylene diamine,N-alkylmorpholines, organometallic salts such as stannous acylates,e.g., stannous dioctoate, dialkylstannic acylates such as dibutyl tindilaurate, acetyl acetonates of heavy metals, e.g., of iron and so on.As emulsifiers one may use, for example, oxyethylated phenols, highersulphonic acids, sulphonated castor oil, sulphonated ricinoleic acid,oleic acid ammonium salts and the like and mixtures thereof. Somesuitable foam stabilizers include those based onpolysiloxane-polyalkylene glycol copolymers, basic silicone oils and thelike. Suitable emulsifiers, catalysts and additives are mentioned, e.g.,in Palyurethanes, Chemistty and Technology, Volumes 1 and 11, Saundersand Frisch, Interscience Publishers, 1962 and 1964, U.S. Pat. No.3,201,372

and so on.

The quantities of polyisocyanate should,,as a rule, be at leastequivalent to the sum of the active hydrogen atoms present. Where foamsare being produced using water as the blowing agent, appropriatequantities of additional polyisocyanates will be used according to thewater content. Excess isocyanate groups in the reaction mixture,optionally in a foamable reaction mixture, can be built into thesynthetic resin structure, preferably into a foam resin structure, inthe form of isocyanurate groups and/or carbodiimide groups by theaddition of, e.g., trivalent or pentavalent phosphorus compounds such asphospholidines, phospholine oxides, tertiary esters, amides or esteramides of phosphorus or phosphoric acid and the like and mixturesthereof.

The products of this invention may be used for many different purposesincluding the production of elastomers, coatings and impregnantsprepared by any of the known methods, if desired, with the inclusion ofinert solvents, polyesters, hydrocarbons, halogenated hydrocarbons andso on. It is preferred to use the process disclosed herein for theproduction of foam plastics. Such foam plastics have a wide range ofapplication due to their flameproof nature, e.g., in the buildingindustry as soundproof materials, for heat insulation, as packagingmaterial for protection against shock and so on. The foam products ofthe instant process may be hard, semihard or flexible and can thereforealso be used as upholstery material. The process of this invention mayalso be used to produce semihard molded polyurethane foams having acompact surface and cellular core which can be sued, for example, ascrash pads in the automobile industry.

The invention is further illustrated but is not intended to be limitedby the following examples in which all parts and percentages are byweight unless otherwise specified.

EXAMPLE 1 a. Preparation of the N-methylol Compounds A. A mixture ofabout 1,900 parts of paraformaldehyde and about 12.5 parts of magnesiumoxide is slowly introduced into a melt of about 1,180 parts of acetamideand the reaction mixture is heated at about C. for about 10 hours. About2,806 parts of a clear liquid is formed in the process and is separatedfrom the solid inorganic constituents.

B. A mixture of about 8 parts of potassium carbonate and about 500 partsof paraformaldehyde is slowly introduced into about 356 parts of moltenethyl carbamate and the reaction mixture is heated at about 100 C. forabout 4 hours. After removal of the solid inorganic constituents, about657 parts of a clear liquid are obtained.

C. About 855 parts of p-toluenesulphonamide and about 1,215 parts of anaqueous formaldehyde solution (40 volume percent) are heated at about100 C. for about 1 hour. The water is distilled off in vacuo. About 900parts of a viscous oil are obtained.

D. Analogous addition products are prepared as described in A (a)substituting equivalent quantities of butyramide or stearoylamide forthe acetamide or (b) substituting equivalent amounts of acetaldehyde,butyraldehyde or azelaic aldehyde about 20 parts oftrichloroethylphosphate and about 10 parts of the N-methylol compound of(a) A. This mixture is intensively stirred together with about 118 partsof a polyphe'nylpolymethylene-polyisocyanate obtained byaniline-formaldehyde condensation followed by phosgenation, whichcomprises 3.2 percent by weight of 2,2'-diisoeyanato diphenyl methane,5,1 percent by weight of 2,4'-diisocyanat'o diphenyl methane, 49,0percent by weight of 4,4'-diisocyanato diphenyl methane, 18,2 percent byweight of trinuclear compounds and 5,7 percent by weight of tetranuclearcompounds and after about 20 seconds it is poured into paper'- molds.After about 2 minutes a hard foam is formed which has the, followingproperties:

1.9 kg. wtS/cm."

0.2 cm. kg. It/cm. dimensionally stable Bulk density Compressionstrength lmpact strength Dimensional stability at 30 C. Combustion testaccording to ASTM-D 1692 noncombustible Complete combustion time in theTorch test 106 seconds Bulk density Compression strenth shrunk beforethe compression test not dimensionally stable Impact strengthDimensional stability at -30 C.

Combustion test according to ASTM-D I692 noncombustible Completecombustion time in the Torch test 63 seconds EXAMPLE 2 A mixture ofabout 80 parts of a polyether obtained from sucrose and propylene oxideand having an OH number of 380, about 20 parts of a flame protectiveagent having the formula Bulk density Compression strength Impactstrength Combustion test according to ASTM-B I692 noncombustibleComplete combustion time in the Torch test -205 seconds Comparison TestIf the process is carried out as described in Example 2 but without theN-methylol compound (in which case the quantity of polyisocyanate usedis reduced to about 94 parts), a hard foam plastic is obtained which hasthe following properties:

Bulk density Compression strength Im act strength Combustion testaccording to ASTM-D I692 noncombustible Complete combustion time in theTorch test I48 seconds It is to be understood that any of the componentsand conditions mentioned as suitable herein can be substituted for itscounterpart in the foregoing examples and that although the inventionhas been described in considerable detail in the foregoing, such detailis solely for the purpose of illustration. Variations can be made in theinvention by those skilled in the art without departing from the spiritand scope of the invention except as set forth in the claims.

What is claimed is:

1. A flame resistant polyurethane prepared from an organicpolyisocyanate, a compound containing at least two hydrogen atomsreactive with NCO groups and a flame retarding additive, whichpolyurethane contains from about 1 to about 20 percent by weight basedon the quantity of the organic polyisocyanate of a N-methylol compoundhaving the struc-' ture:

O O O O O wherein R" is an alkyl radical having I to 18 carbon atoms. Ris an aryl radical having six to 14 carbon atoms, R and R are hydrogenor an alkyl radical having one to four carbon atoms and n is an integerof l to 3.

2. The polyurethane of claim 1 having a cellular structure.

3. The polyurethane of claim 1 wherein the N-methylol compound isprepared from paraformaldehyde and acetamide.

4. The polyurethane of claim 1 wherein the N-methylol compound isprepared from paraformaldehyde and ethyl carbamate.

5. The polyurethane of claim 1 wherein the N-methylol compound isprepared from formaldehyde and p-toluene sulfonamide.

6. The polyurethane of claim 1 wherein the flame retarding additive hasthe structure HO-CHz-CH: O-CzH;

N-CHr-fi HO-CHrCHz O O-CzHs 7. The polyurethane of claim 1 wherein theN-methylol compound is present in an amount offrom about 1 to about 15percent by weight based on the organic polyisocyanatei lOl024 0587

2. The polyurethane of claim 1 having a cellular structure.
 3. Thepolyurethane of claim 1 wherein the N-methylol compound is prepared fromparaformaldehyde and acetamide.
 4. The polyurethane of claim 1 whereinthe N-methylol compound is prepared from paraformaldehyde and ethylcarbamate.
 5. The polyurethane of claim 1 wherein the N-methylolcompound is prepared from formaldehyde and p-toluene sulfonamide.
 6. Thepolyurethane of claim 1 wherein the flame retarding additive has thestructure
 7. The polyurethane of claim 1 wherein the N-methylol compoundis present in an amount of from about 1 to about 15 percent by weightbased on the organic polyisocyanate.